Eurogamer has posted an article-style interview with Chris Avellone, going into significant detail about Avellone's story regrets for Knights of the Old Republic II: The Sith Lords, but perhaps more interestingly, it also touches on the fact that Knights of the Old Republic III was indeed in pre-production at Obsidian, but never saw the light of day. Many story elements in The Sith Lords were intended to lead into that sequel that never happened.
"There's a lot of design decisions that occurred in Knights of the Old Republic 2 that, to this day, I still question whether that was the right thing to do or not, and one was, ideally we should have maybe looked for more ways to introduce Revan in the sequel. It's a surprisingly lengthy and interesting feature, so we recommend anyone interested in the Knights of the Old Republic games take a look for themselves.
"But then again," he adds, "when we were plotting out the idea of doing the third game we just thought it would be cool if we were foreshadowing what Revan was really doing in Knights of the Old Republic 1, and what he was preparing for in Knights of the Old Republic 2, and then bring it to a close, the end of the trilogy, but we didn't get a chance to do that."
"The entire second game is littered with clues as to 'why didn't Revan destroy the infrastructure here? What was he trying to make sure was still intact? What did he/she see that no one else saw?' I thought that was giving a nice nod to 'wait a minute, Revan realises there's an even larger force at work here, and he's focusing his efforts on that and keeping the big picture in mind'. That was one thing - the idea that there was a larger, global conspiracy."
That third game would cast you as "the Exile" and allow you to track Revan's path. "Whether you encounter him or not..." he pauses, wary of spoilers in case the game ever happens in the future. "The idea was that even before the 'modern day' Sith came into being in The Old Republic ... there were even more distant Sith Lords that were considered the true Sith, and the idea that they were still lurking out there in the galaxy waiting for a chance to strike, kind of like the Shadows in Babylon 5, I thought would be a cool finale for that Old Republic trilogy.